Alfalfa hay-Grasshopper

Includes several species, especially Melanoplus spp.

Pest description and crop damage Both nymphs and adult grasshoppers feed on foliage. Early management of grasshopper populations is critical. Consider treatment when populations exceed 8 adults or large nymphs or 12 small nymphs per yard. For additional information, see: https://www.agronomy.org/files/publications/alfalfa-management-guide.pdf.

Management-chemical control

Most of the following insecticides are hazardous to bees and should not be used if bees are foraging in the alfalfa.

  • alpha-cypermethrin (Fastac EC) at 0.0175 to 0.025 lb ai/a. PHI 3 days of cutting or grazing. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.075 lb ai/a per season.
  • beta-cyfluthrin (Baythroid XL) at 0.0155 to 0.022 lb ai/a. PHI 7 days for grazing or cutting. REI 12 hr. Retreatment interval 5 days. Do not exceed 0.044 lb ai/a per cutting or 0.175 lb ai/a total per season. (Group 3A)
  • chlorantraniliprole/lambda-cyhalothrin (Besiege) at 0.059 to 0.088 lb ai/a. PHI 1 day for forage and 7 days for hay. REI 24 hr. Minimum of 5 days between applications. Do not exceed 0.12 lb ai of products containing lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole-containing foliar products per acre per growing season. Refer to product labels for application limits if products containing gamma-cyhalothrin and products containing lambda-cyhalothrin are to be used in the same season. (Groups 28 and 3A)
  • chlorpyrifos (numerous products) at 0.25 to 0.5 lb ai/a. PHI for grazing or cutting is 7 days at 0.25 lb ai/a or 14 days at 0.5 lb ai/a or 21 days for rates above 0.5 lb ai/a. REI 24 hr. Do not apply any chlorpyrifos products more than four times per season or more than once per cutting. Do not reapply within 10 days of the first application. Certain products can be chemigated by sprinkler irrigation. Minor phytotoxicity is possible on new growth. (Group 1B)
  • chlorpyrifos/gamma cyhalothrin (Cobalt) at 0.14 to 0.26 lb ai/a. PHI 14 days. REI 24 hr. Do not apply Cobalt nor any other product containing chlorpyrifos more than once per cutting nor more than 4 times per season. Refer to product labels for application limits if products containing gamma-cyhalothrin and products containing lambda-cyhalothrin are to be used in the same season. (Groups 1B and 3A)
  • cyfluthrin (Tombstone) at 0.031 to 0.044 lb ai/a. PHI 7 days for grazing or cutting. REI 12 hr. Retreatment interval 5 days. Do not exceed 0.088 lb ai/a per cutting or 0.35 lb ai/a total per season. (Group 3A)
  • diflubenzuron (Dimilin 2L) at 0.016 to 0.031 lb ai/a. PHI 1 day for forage or hay. REI 12 hr. Do not exceed 1.5 oz ai/a per season. Limit 3 treatments. Addition of a crop oil or methylated seed oil improves efficacy.
  • dimethoate (numerous products) at 0.25 to 0.5 lb ai/a. PHI 10 days for grazing or cutting. REI 48 hr. Suppression only. Do not apply during bloom. Apply only once per cutting. Effective only on the cutting to which it is applied. PHI 10 days for harvest or grazing. Do not exceed 0.5 lb ai/a per season. (Group 1B)
  • gamma-cyhalothrin (Declare) at 0.01 to 0.015 lb ai/a. PHI 1 day for forage harvest or 7 days for hay harvest. REI 24 hr. Do not exceed 0.015 lb ai/a per cutting or 0.06 lb ai/a per season. Refer to product labels for application limits if products containing gamma-cyhalothrin and products containing lambda-cyhalothrin are to be used in the same season. (Group 3A)
  • indoxacarb (Steward supp label) at 0.039 to 0.059 lb ai/a. PHI 7 days for grazing or cutting. REI 12 hr. Do not exceed one application per cutting or 0.44 lb ai/a per season. (Group 22A)
  • lambda-cyhalothrin (Warrior II) at 0.02 to 0.03 lb ai/a. PHI 1 day for forage harvest or 7 days for hay harvest. REI 24 hr. Apply only to pure stands. Do not apply when bees are actively foraging. Do not exceed 0.03 lb ai/a per cutting or 0.12 lb ai/a per season. Refer to product labels for application limits if products containing gamma-cyhalothrin and products containing lambda-cyhalothrin are to be used in the same season. (Group 3A)
  • malathion (numerous products) at 1 to 1.25 lb ai/a. PHI 0 days. REI 12 hr. Not effective below 65°F. Retreatment interval 14 days. Limit to 2 applications per cutting. (Group 1B)
  • Nosema locusta (pathogenic protozoan) (Nolo Bait)-Apply as manufacturer directs. OMRI-listed for organic use.
  • phosmet (Imidan 70-W) at 0.7 to 1 lb ai/a. PHI 7 days for grazing or cutting. REI 5 days. Do not apply more than once per cutting. Do not apply during bloom. Do not use latex- or pineolene-based adjuvants. (Group 1B)
  • zeta-cypermethrin at 0.035 to 0.05 lb ai/a (Mustang), or at 0.0175 to 0.025 lb ai/a (Mustang Max EC or Mustang Maxx). PHI 3 days for cutting or grazing, 7 days for seed. REI 12 hr. Retreatment interval 7 days. Do not use more than 0.025 lb ai/a per cutting or more than 0.075 lb ai/a per season. (Group 3A)